This application is directed to methods for detecting the presence of, absence of, or amount of, a target analyte (e.g., a material of interest) in a biological sample.
Methods for detecting analytes in a sample and for determining the chemical composition of a sample are useful in many clinical and scientific applications. A method for identifying, or for quantifying the amount of, a substance or substances in a sample may be termed an “assay.” Assays typically include a step, or series of steps, applied to a sample in order to identify or quantify a sample, or a substance or substances in a sample. Assays typically include steps of contacting a sample with a reagent, and of detecting a signal indicative of the presence or absence, or of the quantity of, an analyte. Some assays are performed by devices or systems designed to perform the assays with little or no human intervention; such assays may be termed automated assays, and are performed by automatic devices or automatic systems.
Clinical assays are often developed to identify target materials in samples taken from patients. For example, targets may include proteins, nucleic acids, lipids, organic molecules, inorganic molecules and ions. Such target materials may include drugs, drug metabolites, vitamins, hormones, growth factors, carrier proteins, cells, infectious agents, and other target materials that may be indicative of medical conditions or disorders.
Many different assays with different advantages (and disadvantages) may be developed that are directed to the same analytes. In addition, the properties and identifying characteristics of samples and of analytes may vary widely; for this reason, assays of various kinds and of differing complexities may be required in order to identify and quantify different targets. Some assays may be better suited for use in identifying protein targets than in identifying nucleic acid targets, for example. Some assays may be better suited for use on automated devices or systems than for performance by hand. Accordingly, some assays may be better suited to different targets, or to different applications, or different methods of performance, than other assays.
Assays for clinically relevant targets take many forms, partly for historical reasons and partly due to the many different chemical and biochemical approaches available to detect and measure the same or similar targets. Different techniques may be used to bind to or otherwise interact with a target, and different techniques may be used to signal such binding or other interactions. For example, binding interactions typically include specific and non-specific binding, which must be distinguished in an assay; in addition, different samples, and different targets, have different amounts and kinds of interfering non-specific binding interactions. Since binding to a target may be by competitive, non-competitive, or uncompetitive mechanisms, different assay strategies and conditions must be determined and used for the different kinds of interactions, or strategies and conditions must be found that are useful for multiple kinds of binding interactions. In addition, the results of any such binding interactions must be detected in order for an assay to be of any use; multiple strategies and techniques are available and may be used for detecting and quantifying binding interactions with target materials in a sample.
Thus, there may be multiple ways to perform an assay; each way may have different advantages and disadvantages. An assay method may have advantages when compared to other assay methods: for example an assay method may be faster, or may be simpler, or may be more readily quantified, than other methods. However, an assay method may have disadvantages when compared to other assay methods; for example an assay method may be more expensive, or slower, or may only provide a signal that is harder to detect or to quantify, than other methods. Typically, an assay method will have some advantages and also have some disadvantages, when compared to other assay methods, and the advantages and disadvantages of an assay may differ when it is performed by automated device or system as compared to the performance of the assay by hand.
In some instances, a sample may include multiple analytes, and multiple assays may be required to detect or quantify all of the analytes of interest in a sample. However, choosing an assay for an analyte from among the many possible alternative assays, and in particular choosing an assay for detecting or quantifying the analyte that is also suitable for use with other assays for other analytes, presents complicated choices.
Each of the different conditions and strategies which may possibly be used in an assay will have different costs, different levels of complexity and difficulty, and different levels of reliability and consistency than other conditions and strategies. For example, some strategies and some assay conditions may be less expensive than others, or may provide quicker results than others; cheaper assays and quicker results may, or may not, be of equal accuracy or reliability as results from other assays that take longer or are more expensive. In general, assays may be improved, e.g., may be altered to provide more accurate, or more reliable, or more rapid, results, or may be altered in order to reduce the costs associated with performing the assay. In general, there are a multitude of possible approaches, ways, and means for improving assays. However, it is often not clear what approach to take, or what ways or means to use, in order to improve an assay.
Accordingly, guidelines and methods for altering assays in order to provide improved assays are needed.